Maize Regulatory Elements for Stable Transgene Co-expression
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Solution Overview
Problem
The repeated use of similar promoters in transgenic plants for co-expression of multiple transgenes can lead to homology-based gene silencing and instability, particularly in Agrobacterium systems, due to recombination and plasmid instability, which affects the expression of desirable traits.
Innovation Solution
The use of purified maize gene regulatory elements, such as the chlorophyll a/b gene promoter, 5′-UTR, intron, and 3′-UTR, are recombined with non-native sequences to create expression vectors that facilitate the stable expression of transgenes by avoiding repetitive sequences and promoting tissue-specific expression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the same promoter is repeatedly used to drive expression of multiple transgenes, then co-expression of multiple transgenes for regulating the same trait is achieved, but homology-based gene silencing occurs frequently
Solution Approach 1:
The patent divides the promoter sequence into multiple segments or uses different promoter variants for each transgene in the stack. By segmenting the promoter function across multiple distinct sequences, the system achieves co-expression of multiple transgenes while avoiding the homology-based silencing that occurs when identical promoters are used repeatedly.
Solution Approach 2:
The patent applies different promoter sequences with specific local characteristics to different transgenes within the stack. Each transgene is paired with a promoter having unique sequence features tailored to its specific expression requirements, thereby achieving versatile co-expression while maintaining stability through sequence diversity.
2Productivity
If repetitive DNA sequences are used within a transgene, then multiple transgenes can be stacked at a single genomic locus, but homology-based gene silencing is triggered
Solution Approach 1:
The patent introduces asymmetry in the DNA sequences of stacked transgenes by using non-identical promoter sequences, different terminators, or modified regulatory elements for each transgene. This asymmetric design allows multiple transgenes to be stacked at a single locus while breaking the symmetry required for homology-based silencing to occur.
Solution Approach 2:
The patent changes key parameters of the transgene constructs, such as promoter sequence composition, terminator sequences, or intron structures, to create sufficient sequence divergence among stacked transgenes. These parameter changes enable efficient stacking while preventing homology-based silencing by ensuring no two transgenes are identical.
3Adaptability or versatility
If similar DNA sequences are used in transgene constructs, then co-expression of multiple transgenes is facilitated, but recombination and plasmid instability occur in Agrobacterium
Solution Approach 1:
The patent extracts only the essential functional elements needed for transgene expression (such as promoter activity, terminator function, and coding sequences) while removing or modifying the repetitive DNA sequences that cause recombination in Agrobacterium. This extraction of core functionality maintains co-expression capability while eliminating the source of plasmid instability.
Solution Approach 2:
The patent uses intermediary sequences or linkers between stacked transgenes that prevent recombination while maintaining functional expression. These intermediary elements act as buffers that separate similar DNA sequences, allowing co-expression of multiple transgenes while preventing the recombination events that would otherwise cause plasmid instability in Agrobacterium systems.
Data Source
AI summary
Provided are vector constructs and methods for expressing a transgene in plant cells and/or plant tissues using gene regulatory elements, including the promoters, 5′-UTRs, introns, and/or 3′-UTRs, isolated from Zea mays.